Generally, a video signal transmitted from a graphics card of a computer is 8 bit data, thus a 256 gray levels can be displayed on each color channel. If the signals for controlling R, G, B on the panel are all 8 bit, the panel is called a 8 bit panel, namely, a true color panel. Since a pixel consists of three color channels of red (R), green (G) and blue (B), each pixel can display 256*256*256 types of colors on the 8 bit panel. However, the existing 8 bit panel is relatively expensive, the process is relatively complex, therefore, most panels are 6 bit, that is, each color channel of most panels can only display 64 grey levels, and as a result, each pixel point of the 6 bit panel can only display 64*64*64 types of colors.
From the above data, it can be seen that physically, the colors displayed by the 6 bit panel are less than 2% of the 8 bit panel. If no processing is performed, the 6 bit display cannot meet people's requirements definitely. The prior art mainly adopts the methods of dithering algorithm and frame rate control for converting a 6 bit panel into an 8 bit panel. The dithering algorithm starts from the perspective of space to perform color enhancement. Whereas the frame rate control starts from the perspective of time to perform processing. These two algorithms are often used together.
For quickly changing images, the dithering algorithm and the frame rate control algorithm can be used to generate more grey levels. The frame rate control algorithm exactly makes use of a plurality of frames of images to simulate the effect of one frame of the original image, thereby displaying more colors. Due to visual inertia of human eyes, the perceived brightness is accumulation of a plurality of frames. The frame rate control algorithm is mixing colors in time, while the dithering algorithm is mixing colors in space. If several pixel points are close to one another, what the eyes perceived from a distance is a color close to an average of these colors, thereby generating some intermedia grey levels. The dithering algorithm exactly increases number of image display grey levels by adjusting the spatial relationship between the pixels.
As panel color enhancement technologies of a liquid crystal display (LCD), the dithering algorithm and the frame rate control algorithm are widely used, which can use a drive integrated circuit with a relatively lower bit width to achieve a display effect with a higher bit width and more rich colors. In the panel display field, in order to increase the response speed of a liquid crystal display and reduce costs, 6 bit controllers are mostly used to control the R, G, B signals respectively, so as to achieve a display effect of 8 bit video data.
Since the conventional dithering algorithm adopts a fixed dithering matrix, this may result in the processed image accompanied with dithering noise, and significant “block effect” may occur. Take the simplest case of displaying a static image as the example, it is assumed that the image data of each frame is the same, the main reason for generating the block effect is the use of a fixed dithering matrix. For each frame, the algorithm performs completely the same processing to the blocks divided by the dithering matrix. Apparently, the image data is the same, the process of the algorithm processing is also the same, hence with respect to any point on the display, the gray level of the same point never changes. Although dithering is performed in space, from the perspective of time, the grey level of the same point stays the same. There is no color mixing in time, which may give people the visual perception of block effect, and result in a relatively bad display performance of the liquid crystal display.
To sum up, when the prior art uses 6 bit controllers to control the R, G, B signals respectively to achieve the display effect of 8 bit video data, the display performance of the display is relatively bad.